Communicate MT changes to impl-only scroll offset animations

cc/animation/scroll_offset_animations.cc

Index: cc/animation/scroll_offset_animations.cc
diff --git a/cc/animation/scroll_offset_animations.cc b/cc/animation/scroll_offset_animations.cc
new file mode 100644
index 0000000000000000000000000000000000000000..7eca7639422a655927a27ba96e37b244ce917c66
--- /dev/null
+++ b/cc/animation/scroll_offset_animations.cc
@@ -0,0 +1,46 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "cc/animation/scroll_offset_animations.h"
+
+#include "cc/animation/animation_host.h"
+
+namespace cc {
+
+ScrollOffsetAnimationUpdate::ScrollOffsetAnimationUpdate(Type type,
+                                                         ElementId element_id)
+    : type_(type), element_id_(element_id) {}
+
+ScrollOffsetAnimations::ScrollOffsetAnimations(AnimationHost* animation_host)
+    : animation_host_(animation_host) {}
+
+ScrollOffsetAnimations::~ScrollOffsetAnimations() {}
+
+void ScrollOffsetAnimations::AddUpdate(ScrollOffsetAnimationUpdate update) {
+  queue_.push_back(update);
+  animation_host_->SetNeedsCommit();
+}
+
+bool ScrollOffsetAnimations::HasUpdatesForTesting() const {
+  return !queue_.empty();
+}
+
+void ScrollOffsetAnimations::PushPropertiesTo(
+    ScrollOffsetAnimationsImpl* animations,
+    base::TimeTicks frame_monotonic_time) {
+  DCHECK(animations);
+  if (queue_.empty())
+    return;
+
+  for (auto& update : queue_) {
+    switch (update.type_) {
+      case ScrollOffsetAnimationUpdate::Type::SCROLL_OFFSET_CHANGED:
+        animations->ScrollAnimationApplyAdjustment(
+            update.element_id_, update.adjustment_, frame_monotonic_time);
+    }
+  }
+  queue_.clear();
+}
+
+}  // namespace cc